Yeah, that might be my fault. In my early hosting days, I did post the roles and rules as soon as sign-ups started. That was kind of the norm. But lately, I've had to fill-in host a bunch and don't really worry about the rules and roles until sign-ups are closed and I have to suddenly figure them up. I'll admit, I've been coasting a lot but somehow, I've come up with a lot of cool stuff and the game usually works. But I'd only recommend that if you are pretty comfortable hosting since after awhile, you figure what will work and what doesn't and how to keep things balanced.
For first time hosts, you may want to post a lot of information before hand since there may be a few questions about the rules and roles. When you procrastinate and post that info all at once, you can get a pile of pm's from players asking the same questions or needing explainations. If you aren't prepared for that, it can be a shock to end up with so many requests at once. Posting ahead will help relieve a bit of that first day wave.
It might help with participation also. I think that if I had figured out how to work the Psyche-locks into my game sooner last time so that everyone was aware about them ahead of time, there would have been more interest and participation.